With the rapid advancement of virtual reality environments which allow fully three-dimensional simulation of a virtual world, there is an increasing need for input devices which allow intuitive control of dimensions beyond the two-dimensional (2D) controls currently offered by a mouse, trackball or joystick.
It is well known that some input devices currently provide three-dimensional (3D) inputs of up to six degrees of freedom (6DoF). That is to say, 3D/6DoF devices enable translational control along the conventional three axes (i.e., X-axis, Y-axis and Z-axis) and rotational control about each of the three axes, commonly referred to as roll, pitch and yaw. These devices currently utilize magnetic, acoustic, infrared and mechanical methods to achieve 3D/6DoF tracking. 3D/6DoF controllers employing mechanical methods are typically utilized in the operation of heavy equipment. These devices must be rugged, accurate and immune from the effects of noise. Accordingly input control devices used for interactive graphics are not suitable for use in field applications. As a result, heavy equipment controllers typically consist of an array of heavy-but-reliable levers which have little if any intuitive relationship to the functions being performed. Such controllers present a non-intuitive user interface and require significant mental agility and experience to operate.
Another type of input control device is found in U.S. Pat. No. 5,146,566 (Hollis et al.) which provides an I/O system for a computer user interface using magnetic levitation. Such a system includes a magnetic levitation device having a matched electrodynamically levitated movable element (referred to as a "flotor") and stator, and an electrodynamic forcer mechanism for receiving coil currents for applying controlled magnetic forces mutual to the flotor and stator. A processor unit, in conjunction with control software, measures the relative movement of the flotor-stator combination and controls the coil currents provided to the electrodynamic forcer mechanism. Magnetic levitation devices, however, are sensitive to electromagnetic interference and are far too expensive to be useful to the average computer owner.
Other 3D/6DoF controllers and systems have also been known to be based on touch or force sensitivity. Examples of such devices can be found in U.S. Pat. No. 5,335,557 (Yasutake) which utilizes forced-based pads to provide a touch sensitive 3D/6DoF input control device and U.S. Pat. No. 4,811,608 (Hilton) which discloses force and torque converters.
U.S. Pat. No. 5,222,400 (Hilton) discloses a force and torque-based 3D/6DoF input device which utilizes optical emitter/detectors (i.e., light emitting diodes and photodiodes). A user applying a force or torque (i.e., a user input) to the input device causes a shutter (i.e., a metal strip) to move. The moving shutter alters the extent to which the radiation of the LEDs can fall on the photodiode and, thus, alters the amount of current relayed to electrical circuitry that is coupled to the photodiodes. The translational and rotational displacement are then determined by measurement of altered current.
These types of force and torque input devices remain fixed to a base and provide 3D/6DoF input as forces and torques are applied to the device by the user. Some users, however, have found these controllers difficult to employ because the operation of such input devices actually involves very little user interaction and motion of the device. Such devices also do not provide direct positional information due to their force and torque-based characteristic.
There is a continuing need for input devices which provide more intuitive 3D/6DoF control using low cost equipment. Further, there is a desire to provide an alternative tracking method, other than those currently employed.
One possible alternative tracking method is vision-based (optical) tracking. Vision-based tracking techniques, however, have been unsuccessful in the past. This is tied to a three point problem which relates to the theory that three reference points are required to track an object in three dimensional space. The problems with vision-based techniques have also been associated with the poor resolution of digital video cameras and algorithms which are not capable of keeping pace with tracked points when the points move at sharp, irregular angles in a short period of time (i.e., lagging).
Accordingly, it is an object of the invention to provide a 3D/6DoF vision-based input device which is physically more compliant than existing devices, thereby allowing for more intuitive user control.
It is a further object of the invention to provide a 3D/6DoF input device which utilizes low cost equipment.
Another object of the invention is to provide a 3D/6DoF controller which can incorporate both velocity and position feedback without the need for force-sensing technology.
It is also an object of the invention to provide a simple 3D/6DoF input device for use with any computer equipped with a camera.
An additional object of the invention provides a 3D/6DoF input device which is insensitive to acoustic or electromagnetic noise.
Another object of the invention is to provide a 3D/6DoF input device which utilizes ordinary light as the tracking medium.